Re: operational F, m, and a (velocity measurements with fish-scal es)

["John S. Denker" <jsd@MONMOUTH.COM>]

At 10:01 AM 10/19/01 -0500, RAUBER, JOEL wrote:

> I'm willing to stipulate an arbitrarily well lubricated excellently
> designed ideal scale.

Good, that simplifies the discussion.  Call that approximation /1/.

> The gamma v term isn't present when you make an ideal reading, as you
> measure v to be zero.

No, I don't.  That's not my definition of ideal.  Maybe YOU insist on
observing v to be zero, but I don't.

>   Or you at least had to measure v to make your corrections.

No corrections are necessary because of approximation /1/.  So once again,
this is not a reason for worrying about v.

> > 4) It may be inconvenient for you to make an observation when
> > the velocity
> > is nonzero, but Hooke's law still applies whether you find it
> > convenient or
> > not.  You can make things more convenient by making a movie
> > and analysing
> > it frame-by-frame later, to find the value of (x) as a
> > function of time....
> > Hooke's law is applicable to any (x), whether or not (x) is constant.
> >
>
> True.  If I understand you correctly, you are saying that in order to use
> the spring scale I do not have to line of the pointer next to the tick marks
> in such a way that their relative velocities are zero.

That's what I'm saying.

> We agree that this is highly incovenient,

OK.

> and not what one does in practice with spring scales;

Maybe it's not what YOU do with spring scales, but you can't require others
to follow the same practices as you.

> However,
>
> a) We are still required to make a velocity measurement (and perhaps even
> acceleration measurements), as a matter of principle in operating the device
> in that matter. I don't think one can escape that reality.

This has been repeatedly asserted, but no experimental evidence or
theoretical support has been given.  Re-asserting it won't help.

I suspect this is an axiomatic assumption in JR's world-view.  If so, we
have nothing to discuss.  I don't want to get into a religious
discussion.  You can make whatever axiomatic assumptions you like;  I don't
have to agree.

> b) I'd even question whether or not you were using the device for an
> equilibrium determination of force.
>
> (If the answer is it is not an equilibrium determination), then that
> terminates the discussion as we are discussing equilibrium determinations
> and whether or not they implicitly involve acceleration (to be discussed
> later).

I'll let you have this both ways.  The spring-scale gives a reading of
force WHETHER OR NOT things are in equilibrium.  Equilibrium has got
nothing to do with it.

Maybe you want to make an equilibrium measurement.  Fine.  Do whatever you
like.  But you cannot prevent me from making equilibrium AND
non-equilibrium measurements.